Soldiers in the war zone are at high risk for potentially significant of emotional and cognitive repercussions resulting from blast impacts in combat zones. Although mild blast-related TBI (mTBI) and Posttraumatic Stress Disorder (PTSD) result in significant disability and are of major public health importance, little is known about the mechanism of these injuries. Our application attempts to integrate three brain imaging methods (DTI, fMRI, and PET) to better understand the neural systems involved in mTBI and PTSD. Diffusion Tensor Imaging (DTI) has shown great initial promise as a technique for understanding the underlying neural structure of both TBI and PTSD. Functional magnetic resonance imaging (fMRI) allows for measurement of the hemodynamic brain response to specific stimuli, such as trauma related content that and has shown efficacy in PTSD. Positron Emission Tomography (PET) allows for the measurement of specific glucose ligands to map neural transmission, this technique has been very productive in determining the neuro biomarkers in PTSD and mTBI. Our aim is to determine neural biomarkers that can differentiate mTBI, and mTBI with PTSD. In the short run, we may be able to develop more exact model for the neural effects of these disorders in our veteran population. In the long run, we hope to determine neural biomarkers that can provide a objective and neural representation of disease course for therapeutic intervention studies. PUBLIC HEALTH RELEVANCE: Project Narrative: In the proposed grant we aim to combine three imaging modalities with psychological and neuropsychological assessments to investigate the relationship between PTSD and mTBI. Veterans who are returning from combat deployment who experience a significant combat related trauma can experience one or both of these conditions. Determination of appropriate treatment and of treatment success depends on appropriate diagnosis which is difficult as there conditions share numerous clinical and behavioral manifestations. Advancements in our understanding can lead directly to better quality of care. Definition and verification of neuropsychiatric biomarkers of these conditions can advance our capacity to measure outcome of clinic interventions (such as in the PI's current CDMRP grant). In this grant, we aim to provide empirical evidence to improve diagnostic approaches and determination of intervention quality so as to have a direct impact on positively shaping healthcare for our veteran's who are suffering combat related injury and stress.